In active matrix display, the crossings of scan lines in rows and data lines in columns form an active matrix. In order to prevent devices on a panel from being damaged by electro-static discharge (ESD) during processes of manufacturing and use, it is necessary to connect an electro-static discharge protection circuit to every data line, for discharging accumulated charges, so as to avoid damage to the devices due to too high voltage pulses.
Currently, there are various kinds of manufacturing process for thin film transistors (TFT) in display apparatus rear panels, for example, amorphous silicon (a-Si) TFT, low temperature poly-silicon (LTPS) TFT and Oxide TFT etc. The Oxide TFT has features of high mobility, good uniformity and low cost, and it is suitable for manufacturing of large size panel. However, due to the restriction to oxide TFT manufacturing itself, the oxide TFT is always of depletion type, i.e. when the gate-source voltage Vgs of a TFT is zero, the drain-source of the TFT is still turned on. The TFT in the conventional ESD protection circuit does not function when the display apparatus is in normal operation at ordinary time, and functions only when static charge occurs. However, if the TFT is of depletion type, the ESD protection circuit still generates drain-source current when the display apparatus is in normal operation at ordinary time. For example, as shown in FIG. 1, when the display apparatus is in normal operation at ordinary time, Vgs for two TFTs is 0V, i.e. Vgs=0V. According to the transmission characteristics of the depletion type TFT, the drain-source of the two TFTs is still continuously turned on, so that a direct current channel from high level output terminal VGH to low level output terminal VGL is formed, resulting in leak electricity from the data line DATA. This affects the output of the data voltage while increasing power consumption.